The M2 Machine Gun

The Browning .50 Caliber Machine Gun is a heavy machine gun designed towards the end of World War I by John Browning. It was nicknamed "Ma Deuce" by US troops or simply called "fifty-cal." in reference to its caliber. The design has had many specific designations; the official designation for the current infantry type is Browning Machine Gun, Cal. .50, M2, HB, Flexible. It is effective against infantry, unarmored or lightly-armored vehicles and boats, light fortifications, and low-flying aircraft.

The Browning .50 caliber machine gun has been used extensively as a vehicle weapon and for aircraft armament by the United States from the 1920s to the present day. It was heavily used during World War II, the Korean War, the Vietnam War, as well as during operations in Iraq in the 1990s and 2000s. It is the primary heavy machine gun of NATO countries, and has been used by many other countries. It is still in use today, with only a few modern improvements. The M2 has been in use longer than any other small arm in U.S. inventory. It was very similar in design to the smaller Browning Model 1919 machine gun.

History

A variant without a water jacket, but with a thicker-walled, air-cooled barrel superseded it (air-cooled barrels had already been used on variants for use on aircraft, but these quickly overheated in ground use). This new variant was then designated the M2 HB ("HB" for "Heavy Barrel"). The added mass and surface area of the new barrel compensated, somewhat, for the loss of water-cooling, while reducing bulk and weight (the M2 weighed convert|121|lb|abbr=on, with water, whereas the M2 HB weighs 84 lb). Due to the long procedure for changing the barrel, an improved system was developed called QCB (quick change barrel). A lightweight version, weighing 24 lb (11 kg) less—a mere 60 lb (27 kg)—was also developed

Design details

The M2 is a scaled-up version of John Browning's M1917 .30 caliber machine gun (even using the same timing gauges), fires the .50 BMG cartridge, which today is also used in high-powered sniper rifles and long range target rifles due to its excellent long range accuracy, external ballistics performance, incredible stopping power, and lethality. The M2 is an air-cooled, belt-fed, machine gun that fires from a closed bolt, operated on the short recoil principle. In this action, the bolt and barrel are initially locked together, and recoil upon firing. After a short distance, the bolt and barrel unlock, and the bolt continues to move rearwards relative to the barrel. This action opens the bolt, and pulls the belt of ammunition through the weapon, readying it to fire again, all at a cyclic rate of 450–600 rounds per minute (600–1,200 M2/M3 in WW2 aircraft, 300 synchronized M2). This is a rate of fire not generally achieved in use, as sustained fire at that rate will "shoot out" the barrel within a few thousand rounds, necessitating replacement. The M2 machine gun's sustained rate of fire is considered to be anything less than 40 rounds per minute.

The M2 has a maximum range of 7.4 kilometers (4.55 miles), with a maximum effective range of 1.8 kilometers (1.2 miles) when fired from the M3 tripod. In its ground-portable, crew-served role, the gun itself weighs in at a hefty 84 pounds (38 kg), and the assembled M3 tripod another 44 pounds (20 kg). In this configuration, the V-shaped "butterfly" trigger is located at the very rear of the weapon, with a "spade handle" hand-grip on either side of it and the bolt release the center. The "spade handles" are gripped and the butterfly trigger is depressed with one or both thumbs. When the bolt release is locked down by the bolt latch release lock on the buffer tube sleeve, the gun functions in fully automatic mode. Otherwise, the M2 is a single-shot weapon. Unlike virtually all other modern machine guns, it has no safety. Conversely, the bolt release can be unlocked into the up position resulting in single-shot firing (the gunner must press the bolt latch release to send the bolt forward). In either mode the gun is fired by pressing the butterfly triggers. Recently new rear buffer assemblies have used squeeze triggers mounted to the hand grips, doing away with the butterfly triggers.

Because the M2 was intentionally designed to be fit into many configurations, it can be adapted to feed from the left or right side of the weapon by exchanging the belt-holding pawls, the belt feed pawl, and the front and rear cartridge stops, then reversing the bolt switch. The conversion can be completed in under a minute with no tools.

There are several different types of ammunition used in the M2HB, including the current types: M33 Ball (706.7 grain) for personnel and light material targets, M17 tracer, M8 API (622.5 grain), M20 API-T (619 grain), and M962 SLAP-T. The latter ammunition along with the M903 SLAP (Saboted Light Armor Penetrator) round can penetrate up to 3/4 inch armor at 1500 meters. This is achieved by using a .30 inch diameter tungsten penetrator. The SLAP-T adds a tracer charge to the base of the ammunition. This ammunition was type classified in 1993.

When firing blanks, a large blank-firing adapter (BFA) must be used to keep the gas pressure high enough to allow the action to cycle. The adapter is very distinctive, attaching to the muzzle with three rods extending back to the base. The BFA can often be seen on M2s during peacetime operations.

Combat use

The M2 .50 Browning machine gun has been used for various roles:
* A medium infantry support weapon
* As an anti-aircraft gun in some ships, or on the ground. The original water-cooled version of the M2 was used as an emplaced or vehicle-mounted anti-aircraft weapon on a sturdy pedestal mount. In some cases multiple air and water-cooled weapons were grouped. In some of these instances the mount featured one M2 with a left-handed feed and one with right-handed feed are paired. Four and six guns are also sometimes mounted on the same turret.
* Primary or secondary weapon on an armored fighting vehicle.
* Primary or secondary weapon on a naval patrol boat.
* Secondary weapon for anti-boat defense on large naval vessels (corvettes, frigates, destroyers, cruisers, etc).
* Coaxial gun or independent mounting in some tanks.
* Fixed-mounted primary armament in World War II-era U.S. aircraft such as the P-47 Thunderbolt, P-51 Mustang, and the Korean-era U.S. F-86 Sabre.
* Fixed or flexible-mounted defensive armament in World War II-era bombers such as the B-17 Flying Fortress, and B-24 Liberator.

United States

At the outbreak of the Second World War the United States had versions of the M2 in service primarily as fixed aircraft guns and as anti-aircraft weapons (mounted on and off a wide variety of vehicles and ships). It was also technically still in service as an anti-tank weapon, as originally intended. ["The American Arsenal", 2001. p. 224] On most of the vehicles the weapon was mounted on it was placed in a position designed for anti-aircraft rather than any other use. Units in the field often modified the mountings on their vehicles, especially tanks and tank destroyers, to be more useful in the anti-personnel role. [Yeide, 2004. p. 185] Reports vary on its effectiveness in this role. There are instances of reports about the "essential" nature of the weapon for anti-personnel uses. [Zaloga, 2002. p. 22]

M2 variants

The basic M2 was deployed in US service in a number of subvariants, all with separate complete designations as per the US Army system. The basic designation as mentioned in the introduction is Browning Machine Gun, Cal. .50, M2, with others as described below.

The development of the M1921 water-cooled machine gun which led to the M2, meant that the initial M2s were in fact water-cooled. These weapons were designated Browning Machine Gun, Cal. .50, M2, Water-Cooled, Flexible. There was no fixed water-cooled version.

Improved air-cooled heavy barrel versions came in three subtypes. The basic infantry model, Browning Machine Gun, Cal. .50, M2, HB, Flexible, a fixed developed for use on the M6 Heavy Tank designated Browning Machine Gun, Cal. .50, M2, HB, Fixed, and a "turret type" whereby "Flexible" M2s were modified slightly for use in tank turrets. The subvariant designation Browning Machine Gun, Cal. .50, M2, HB, Turret was only used for manufacturing, supply, and administration identification and separation from flexible M2s.

A number of additional subvariants were developed after the end of the Second World War. The Caliber .50 Machine Gun, Browning, M2, Heavy Barrel, M48 Turret Type was developed for the commander's cupola on the M48 Patton tank, and then later used in the commander's position on the M1 Abrams tanks. Three subvariants were also developed for used by the US Navy on a variety of ships and watercraft. These included the Caliber .50 Machine Gun, Browning, M2, Heavy Barrel, Soft Mount (Navy) and the Caliber .50 Machine Gun, Browning, M2, Heavy Barrel, Fixed Type (Navy). The fixed types fire from a solenoid trigger and come in left or right hand feed variants for use on the Mk 56 Mod 0 dual mount and other mounts.

AN/M2, M3, XM296/M296, and GAU-10/A

The M2 machine gun was heavily used as a remote fired fixed weapon, primarily in aircraft, but also in other applications. For this a variant of the M2 was developed (sometimes seen under the designation AN/M2, but it is important to note that there were .30 and .50 caliber weapons with this designation), with the ability to fire from a solenoid trigger. For aircraft mounting some were also fitted with substantially lighter barrels, permitted by the cooling effect of air in the slip-stream. The official designation for this weapon was Browning Machine Gun, Aircraft, Cal. .50, M2 followed by either "Fixed" or Flexible" depending on whether the weapon was used as a fixed forward firing gun or for use by an airplane's crew.

The Hispano 20mm Cannon

 

The Hispano Suiza 20 mm cannon was one of the most widely used aircraft weapons of the 20th century, used by British, American, French, and many other military services.

This cannon was based on the earlier Swiss Oerlikon HS.7/HS.9 weapons, which Hispano Suiza manufactured under license. In the late 1930s engineer Mark Birkgit designed a new and much improved version with a revised action, faster rate of fire, and higher muzzle velocity. This entered service as the HS Type 404. This was adopted by the RAF and FAA in 1941 as the Hispano Mk II and by the U.S. as the M1 and incrementally improved M2 (although American-made weapons had minor production differences that made them notably less reliable than their British counterparts). It was primarily used by the U.S. Navy. The British upgraded to the Mk V, which was lighter and had a higher rate of fire, and the U.S. followed suit with the M3. After World War II the USAF adopted a version of the M3 cannon as the M24, similar in most respects except for the use of electrically primed ammunition.

The Hispano fired a 130 gram (4.59 oz) 20 mm x 110 mm projectile with a muzzle velocity between 840 and 880 m/s (2,755 and 2,888 ft/s), depending on barrel length. Rate of fire was between 600 and 850 rounds per minute. It was 2.36 m (7 ft 9 in) long, weighing between 42 and 50 kg (93 and 110 lb). The British Mk V and American M3/M24 weapons were lighter with higher rates of fire than the early HS 404 guns.

See hear for problems associated with the Hispano cannon

 

Remote turret

The XP-61's spine-mounted dorsal remote turret could be aimed and fired by any one of the three-man crew, or could be locked forward to be fired by the pilot in addition to the 20 mm (.79 in) cannons. The radar operator could rotate the turret to face to the rear, in order to engage targets behind the aircraft. Capable of a full 360° rotation and 90° elevation, the turret could conceivably be used to engage any target in the entire hemisphere above and to the sides of the XP-61. The turret had buffeting problems on the airframe and wasn't installed for a few production runs.

HVAR

The 5-inch FFAR suffered from insufficient speed because of its small motor. Therefore the development of a larger rocket motor with 5-inch diameter was begun, and the first test firings occurred in December 1943. When fitted with the warhead of the 5-inch FFAR, the rocket achieved a velocity of 1530 km/h (950 mph), making it a very powerful weapon for its time. It was officially designated as 5-Inch HVAR (High-Velocity Aircraft Rocket), but often called Holy Moses. It became operational in July 1944, and was used by Army Air Force and Navy aircraft.

During World War II, two versions of Holy Moses were built, one general-purpose with base and nose fuzes, and one with a semi-armour-piercing warhead and a nose fuze only. Postwar developments added a shaped-charge anti-tank warhead, and a new general purpose type with a proximity fuze. More than one million Holy Moses HVARs were built until production ended in 1955.